The present invention relates to an apparatus for shaping plastics material pre-forms into plastics material containers. Machines of this type have long been known from the prior art, or example in the form of stretch blow moulding machines. These machines usually have a rotatable carrier on which a plurality of shaping stations are arranged. In the individual shaping stations the heated plastics material pre-forms are stretched by means of a stretch bar driven in a linear manner and expanded in blow moulds by a gaseous medium and, in particular, compressed air. Specific products such as fruit juice beverages or milk beverages require as aseptic a filling as possible in order to achieve the necessary minimum shelf life. One possibility of implementing this is the sterile production of the plastics material containers used for the filling. In this case it is necessary to supply the blow moulding stations with sterile compressed air. This sterile compressed air acts in this case as a shaping medium for the plastics material containers.
An apparatus and a method of cleaning gas in blow moulding machines is known from EP 2 388 128 12. In this case at least one gas line, which can be a gas supply line or a gas removal line to or from a blow moulding station, has arranged in it at least one gas preparation device which is capable of filtering gas in a sterile manner and/or of reducing a quantity of an oxidative disinfection or sterilization agent contained in the gas flowing through and/or flowing past.
It is customary in the prior art for compressed air from a compressed air source to be conveyed out of the stationary portion of the machine by way of a distributor device (such as for example a rotary distributor) into the rotating portion of the machine, i.e. a turntable. In this rotating portion of the machine the compressed air is usually supplied from the distribution device to pressure reduction units. These pressure reduction units prepare the compressed air for different pressure levels required for the shaping process. In this case the pressure reduction units are designed for example in the form of compact sub-assemblies with dome-loaded pressure regulators and attachment apparatuses for the compressed air inlet and the compressed air outlet.
Within the scope of the invention it is possible in this case for these pressure reduction units to be arranged in the form of a star around the distribution device in the peripheral direction and optionally also to be directly attached to the distribution device by way of a flange connection. Further, it is also possible for the compressed air to be supplied at different pressure levels from reduction units to various annular ducts by way of hose lines. These annular ducts distribute the compressed air to the blow moulding stations.
In addition, as well as the supply of the individual shaping stations with compressed air as the shaping medium of the plastics material containers in the rotating portion of the machine, it is also customary for control air to be produced at different pressure levels and with different tasks. This control air is required for example in order to switch valves in the blow moulding station. In this case the control air is usually branched off from the blowing air line in the rotating portion of the machine and is reduced to the necessary pressure levels by reduction devices.
A drawback of this design is that it is frequently difficult in this case to ensure a sterile supply of blowing air. In particular, in the blowing air line the seals of the components tone another and the connections of the hose lines for the attachments thereof are a potential source of contamination of the blowing air. The seals are designed in the form of conventional O-ring and quad-ring seals. In the gaps between these rubber seals and the associated groove it is possible for micro-organisms to multiply and contaminate the blowing air.
The use, in particular, of very hot sterilization agents is again problematic for the valves present in the control air line.
The object of the present invention is therefore to improve the supply with sterile blowing air in blow moulding machines of this type.